The clinical performance of current orthopaedic and dental implant coatings, osteobiologic (bone-filling) materials and pharmaceutical delivery systems is known to be inadequate.
The strength, integrity and osteoconduction properties of an implant/bone interface partly determine the operational life and overall performance of implants. At present, many of the materials in the art have poor osteoconduction.
The regeneration of a patient's own bone into a void is the ultimate desire of patents who require bone correction, repair or replacement. This is primary clinical goal that is not completely achievable with current technologies.
Art-skilled workers have only recently begun to develop synthetic or semi-synthetic materials for orthopaedic coatings and bone filling systems. Current technologies do not permit suitable bone integration or regeneration for either permanent integration of metal implants, or generation of new bone in void sites.
Inorganic materials constitute the mineralized frameworks that shape mammalian skeletons with the primary building block being calcium phosphate in the crystalline form hydroxycarbonate apatite (HCA) or approximated by hydroxyapatite (HA). An ageing demographic is responsible for increasing numbers of joint, tooth and bone replacement therapies being performed internationally. When bones or joints are worn, damaged, diseased or removed, the body loses the ability to repair the site. At this point artificial assistance in the form of implants must be employed. Biomaterials science has determined that a number of conditions are necessary for an implant to be successfully integrated into the skeleton. These conditions include: composition, solubility, porosity, surface chemistry and mechanical strength, but no materials simultaneously possess all of these characteristics.
The identification of soluble amorphous silicate-phosphate glasses (such as Bioglass®) in the 1980's provided a new stimulus to orthopaedic implant and osteobiologic research. The bioglass-type systems however continue to lack pore systems, are only partially resorbable and are significantly more brittle than bone. These characteristics highlight the major failings of implant coatings and bone-filling implants made from HA and Bioglass® to date. Surgeons are also increasingly being restricted in their use of autografts and allografts on comfort, cost and accessibility grounds.
In the past two years, new developments in orthopaedic and osteobiologic bone healing have occurred in the administration of growth factor proteins with implants for the augmentation of bone growth rates at surgical sites. It is likely that incorporation of growth factor proteins into coating or implant materials will stimulate rapid osteogeneration. This burgeoning new area is emerging concurrently with interesting new developments in the area of inorganic porous materials used in general pharmaceutical delivery.
At present, one of the major implant failures is caused by post-insertion loosening due to lack of interaction with the bone of the implant coating.
However, as these materials lack bioactivity, a fibril tissue layer is generated by the living body to isolate the implant materials from the natural tissue and screws, cements or locking systems are needed to secure the implant. In order to stimulate the incorporation of tissue to the implant, some bioactive materials, such as calcium phosphate, are applied to the surface of implant.
Such coatings have achieved certain success over the past several decades in stimulating early post surgical recovery and tissue incorporation, but two major problems limit their clinical use and commercial application. The first problem is the fragmentation of the coatings due to the brittle nature of the coating material and the second problem is the dissolution of the coating materials by the body fluid, leading to coating failure.
It is an object of the present invention to address the foregoing problems or at least to provide the public with a useful choice.
Further, or alternatively, an object of the present invention may be to provide a biomaterial that overcomes at least some of the above-mentioned disadvantages of the above-mentioned biomaterials and/or to provide a process for the production of the above-mentioned biomaterials, or at least to provide the public and/or industry with a useful choice.
All references, including any patents or patent applications, cited in this specification are hereby incorporated by reference. No admission is made that any reference constititutes prior art. The discussion of the reference states what their authors assert, and the applicants reserve the right to challenge the accuracy and pertiency of the cited documents. It will be clearly understood that, although a number of prior art publications are referred to herein, this reference does not constitute an admission that any of these documents forms parts of the common general knowledge in the art, in New Zealand or in any other country.
It is acknowledged that the term ‘comprise’ may, under varying jurisdictions, be attributed with either an exclusive or an inclusive meaning. For the purpose of this specification, and unless otherwise noted, the term ‘comprise’ shall have an inclusive meaning—i.e. that it will be taken to mean an inclusion of not only the listed components it directly references, but also other non-specified components or elements. This rationale will also be used when the term ‘comprised’ or ‘comprising’ is used in relation to one or more steps in a method or process.
Further aspects and advantages of the present invention will become apparent from the ensuing description which is given by way of example only.